Study Of Gas Solid Interactions During Sintering Of Cr-Containing PM Steels

摘要

Several atmospheres including Ar, N_2, and N_2-H_2 blends, with occasional additions of CH_4 were studied in relation to the sintering behaviour of AsCrM at temperatures of 1100 and 1240℃. Theoretical thermodynamic calculations and sintering experiments, using admixed graphite additions between 0% and 0.8%, were carried out paying particular attention to the reduction of oxides and the carburisation-decarburisation phenomena. The microstructural observation of the material included inspection of the powder particles to characterise the internal oxides, both, directly and by carbon extraction replicas. The microstructure of as-sintered samples has been studied on cross sections analysed under the optical and the SEM. Hardness measurements and final carbon determination after sintering were also performed. A selection of powder mixtures containing 0 and 0.4% C additions were used for obtaining tensile specimens in order to assess neck development, by the mechanical properties and observation of the fracture surfaces, under the various atmospheres and temperature combinations.